Final answer:
The mechanism of survival in the first experiment is plasmid-mediated resistance, where the resistance to gentamicin and ampicillin is transferred through plasmids.
Step-by-step explanation:
The mechanism of survival in the first experiment where the colony of bacteria resistant to gentamicin and the colony resistant to ampicillin were mixed on an agar plate containing both antibiotics and bacterial growth was observed after incubation for 24 hrs is d) Plasmid-mediated resistance. Plasmids are small, circular DNA molecules that can be transferred between bacteria through conjugation, a process where genetic material is transferred from one bacterium to another. In this case, the resistance to gentamicin and ampicillin in the colonies is transferred through plasmids, allowing the bacteria to survive and grow in the presence of antibiotics.